Phenylketonuria (PKU)

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Causes

By Mayo Clinic staff

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Illustration showing autosomal recessive inheritance pattern Autosomal recessive inheritance pattern

A genetic mutation causes PKU. The defective gene contains the instructions for making an enzyme needed to process the amino acid called phenylalanine. Amino acids are the building blocks for protein. In a person with PKU, this gene is defective, causing a complete or near-complete deficiency of the enzyme. Without the enzyme necessary to process phenylalanine, a dangerous buildup of this amino acid can develop when a person with PKU eats foods that are high in protein, such as milk, cheese, nuts or meats. This can eventually lead to serious health problems.

For a child to inherit PKU, both the mother and father must have and pass on the defective gene. This pattern of inheritance is called autosomal recessive. It's possible for a parent to have the defective gene, but not have the disease. This is called being a carrier. Most often, PKU is passed to children by parents who are carriers of the disorder, but don't know it.

Risk factors Symptoms
References
  1. Phenylketonuria. Genetics Home Reference. http://ghr.nlm.nih.gov/condition=phenylketonuria. Accessed Oct. 6, 2011.
  2. Blau N, et al. Phenylketonuria. The Lancet. 2010;376:1417.
  3. Bodamer OA. Overview of phenylketonuria. http://www.uptodate.com/home/index.html. Accessed Oct. 6, 2011.
  4. PKU (Phenylketonuria). March of Dimes. http://www.marchofdimes.com/baby/birthdefects_pku.html. Accessed Oct. 6, 2011.
  5. Ten Hoedt AE, et al. Parenting a child with phenylketonuria or galactosemia: Implications for health-related quality of life. Journal of Inherited Metabolic Diseases. 2011;34:391.
  6. Van Spronsen FJ, et al. Large neutral amino acids in the treatment of PKU: From theory to practice. Journal of Inherited Metabolic Diseases. 2010;33:671.
DS00514 Nov. 17, 2011

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